1. Field
The present application relates generally to the involvement of Pdia4 in cell growth and cell proliferation, and methods of diagnosing cancer associated with the presence and/or amount of Pdia4.
2. Description of the Related Art
Polyynes are a group of organic compounds with two or more carbon triple bonds. So far, over 1000 polyynes have been isolated from plants, fungi, bacteria and corals (Shi Shun, A. L., et al. (2006) Angew. Chem. Int. Ed. Engl. 45(7), 1034-1057). Polyynic compounds have a variety of biological activities. Many of them have been shown to have a broad range of medicinal and biological properties such as anti-tumor, anti-inflammation, anti-angiogenetic, anti-diabetic, anti-microbial, anti-viral, anti-protozan, and phototoxic activities (Shi Shun, A. L., et al. (2006) Angew. Chem. Int. Ed. Engl. 45(7), 1034-1057; Dembitsky, V. M. (2006)Lipids 41(10), 883-924). More than 300 polyynes have been reported to show cytotoxic activity against a variety of tumor cells (Dembitsky, V. M. (2006)Lipids 41(10), 883-924). However, their anti-tumor mechanism is poorly studied.
Two linear chain polyynes of Bidens pilosa, cytopiloyne (CP) and its aglycone (CPA), inhibit T cell proliferation and induce apoptosis of umbilical vein endothelium cells. CP and CPA belong to a subclass of polyynes with a linear chain structure of four conjugated triple bonds (Wu, L. W., et al. (2004)Pharm. Res. 21(11), 2112-2119; Chiang, Y. M., et al. (2007) J. Ethnopharmacol. 110(3), 532-538). Both compounds were initially identified from Bidens pilosa plant with a cytotoxic activity against leukemia and carcinoma (Sundararajan, P., et al. (2006)Afr. Health Sci. 6(1), 27-30; Chang, J. S., et al. (2001) Am. J. Ch. Med. 29(2), 303-312). CP inhibits T-cell proliferation (Chang, C. L., et al. (2007) J. Immunol. 178(11), 6984-6993), and CPA promotes apoptosis of endothelial cells and in turn, angiogenesis, via disruption of cell cycle (Wu, L. W., et al. (2004)Pharm. Res. 21(11), 2112-2119; Wu, L. W., et al. (2007)Planta Med. 73(7), 655-661). But anti-tumor effect and mechanism of CP derivatives are poorly understood.
Protein disulfide isomerases (PDIs) constitute a family of enzymes which catalyze oxidation and reduction of disulfide bonds during the formation of newly synthesized proteins and help protein folding. PDIs also act as chaperone and most of the PDIs are located in the lumen of the endoplasmic reticulum (ER), but some PDIs are located on other cellular compartments. The family of PDIs play role in mammalian development and diseases (Ni, M., et al. (2007) FEBS letters 581(19), 3641-3651). They possess endoreticulum (ER) functions, e.g., formation and exchange of disulfide bonds during protein synthesis and folding. Besides, they have non-ER functions probably via conformational maintenance of specific proteins, which are implicated in pathogen infection (Ou, W., et al. (2006)Virology 350(2), 406-417; Naguleswaran, A., et al. (2005) Int. J. Parasitol. 35(13), 1459-1472), fertilization (Ellerman, D. A., et al. (2006)Developmental cell 10(6), 831-837), coagulation (Manukyan, D., et al. (2008) Thrombosis research 122 Suppl 1, S19-22), immunity (Garbi, N., et al. (2006)Nat Immunol 7(1), 93-102), tumor metastasis (Goplen, D., et al. (2006)Cancer research 66(20), 9895-9902) or cell viability/growth (Li, X. A., et al. (1991) Molecular and cellular biology 11(7), 3446-3453; Severino, A., et al. (2007) J Am Coll Cardiol 50(11), 1029-1037; U.S. Pat. Pub. No. 2003/0152565). PCT publication WO2010/004214 relates to a method for the in vitro diagnosis of colorectal cancer by determining the presence of the protein disulfide isomerase tumor marker through the use of at least one anti-PDI monoclonal antibody against a PDI epitope. Cellular localization of some PDIs was found in cytosol (ER) and unusual compartments (cell surface, nucleus, etc.). This localization might be related to the ER and non-ER functions (Turano, C., et al. (2002)Journal of cellular physiology 193(2), 154-163. The role of PDIs in cell growth is poorly studied, not to mention the mechanism by which PDIs regulate cell growth. Probably, yeast study comes to the clearest conclusion indicating that PDIs are essential for cell viability (Farquhar, R., et al. (1991) Gene 108(1), 81-89) and the function of all 5 yeast PDIs may not be interchangeable (Norgaard, P., et al. (2001) J. Cell Biol. 152(3), 553-562). Consistently, a general PDI inhibitor, bacitricin, was shown to cause tumor cell death (Lovat, P. E., et al. (2008)Cancer Res. 68(13), 5363-5369). However, mice deficient in Pdia3 were shown to be lethal at embryonic stage (Garbi, N., et al. (2006)Nat Immunol 7(1), 93-102), suggesting that some PDIs may be functionally not redundant.
In mammals, the 9 PDI members are involved in a broad range of cell functions. There are 9 PDI members containing 1 to 3 CGHC active sites in human. The PDIs have been proposed to have different redox potentials, which act sequentially on nascent protein, or distinct substrate specificity in the protein folding process (Maattanen, P., et al. (2006) Biochem Cell Biol 84(6), 881-889). Among the 9 human PDIs, Pdia-4 is the only PDI member with 3 CGHC motifs (Maattanen, P., et al. (2006)Biochem Cell Biol 84(6), 881-889). Pdia4 was reported to be implicated in the unfolded protein response in the ER and acts as chaperone of calcium-binding properties. Up-regulation of Pdia4 was found in highly metastatistic HCC cell lines. In addition, up-regulation of Pdia4 also occurs when DG44 cells were treated with ionophore which causes ER stress. Little is known about the biological role of Pdia4. The expression of Pdia4 whose promoter contains ER stress responsive element could be induced by ER stress (Parker, R., et al. (2001)Molecular and cellular biology 21(9), 3220-3233; Li, X. A., et al. (1991) Molecular and cellular biology 11(7), 3446-3453). Pdia4 and other ER proteins such as Hspa5, Hsp90β1, Pdi, Calr, and Cabp 1 were found to associate with different nascent proteins in ER (Kuznetsov, G., Chen, L. B., and Nigam, S. K. (1994) The Journal of biological chemistry 269(37), 22990-22995; Feng, W., et al. (1995) The Journal of biological chemistry 270(20), 11851-11859; Vandenbroeck, K., et al. (2006) Cytokine 33(5), 264-273). Pdia4 appeared to complex with Hspa5 as well as Hsp90β1. Expression decrease of Pdia4, Hspa5 and Hsp90β1 by the amplification of ER stress responsive element in CHO cells decrease cell growth and viability (Li, X. A., et al. (1991) Molecular and cellular biology 11(7), 3446-3453). Despite a possible link between Pdia4 and cell growth and viability, little is known about the gene function of Pdia-4 in cell growth and viability.
Acute lymphocytic leukemia (ALL) is the most common cancer of childhood. Its incidence rate was 1.6 per 100,000 men and women per year in United States. Around 15% of acute lymphocytic leukemia cases are T cell acute lymphocytic leukemia (T-ALL), a disease caused by malignant transformation of T cells (Grabher, C., et al. (2006)Nat. Rev. Cancer 6(5), 347-359). T-ALL pathogenesis is related to genetic alterations or aberrant expression of oncogenes or tumor suppressor genes. Though treatment outcomes for T-ALL have been much improved, novel lead compounds for T-ALL are necessary. Jurkat cells, which were established from a patient with T cell acute lymphocytic leukemia, are a physiologically relevant tumor model of T-ALL (Gillis, S., et al. (1980) J. Exp. Med. 152(6), 1709-1719).
In chemical biology, small-molecule compounds are used as tools to explore the impact and mechanism of biology (Spring, D. R. (2005) Chem. Soc. Rev. 34(6), 472-482). The key step to chemical biology study is target identification of the compounds, which is the hardest task, too. This identification helps discover new druggable genes, expand the signaling network and understand the action of compounds (Burdine, L., et al. (2004) Chem. Biol. 11(5). 593-597).
There is a need in the art to determine the molecular targets of CP and CPA in vivo and the likely mechanism of the polyynes for the production of screening methods and research tools.